Preparation Of CuCr Alloy Vacuum Contact Materials By High Energy Ball Milling

With the developing of the vacuum switch,which toward to the large capacity,high voltage,miniaturization of the development stage,the research of improving the vacuum switch contact material properties has been widespread concern.Cu-Cr alloy has the advantages of high compressive strength,good breaking performance,strong current erosion resistance,small current cut-off value and so on.It is the material of choice for vacuum switch contact materials.However,Cu and Cr are almost immiscible,and the preparation of Cu-Cr contact materials is difficult because of the severe segregation and coarse structure of the alloys.The application range of Cu-Cr contact materials is limited.Therefore,it is very important to improve the homogeneity and refinement of the Cu-Cr alloy structure and optimize the preparation process to obtain Cu-Cr contact material which meets the performance requirements.In this study,Cu-Cr alloy contact material was prepared by high-energy ball milling combined with liquid phase sintering.The pre-alloying method and the gradient structure preparation method are proposed to optimize the production process and improve the material performance.Microstructure and mechanical properties of Cu-Cr powder and liquid-phase sintered Cu-Cr alloy were investigated by means of scanning electron microscopy(SEM),transmission electron microscopy(TEM),X-ray diffraction(XRD)and differential scanning calorimetry(DSC)The microhardness,tensile properties,density and electrical conductivity of Cu-Cr alloy were measured and analyzed.The influences of the important process parameters on the microstructure,structure,composition and properties of the materials during high energy ball milling and liquid phase sintering were studied.The research contents and results are as follows:Preparation of Cu-Cr alloy contact material by pre-alloying method.The Cu-95%Cr powder was pretreated by high-energy ball milling,and the particles of Cu and Cr were refined with the milling time prolonged.After 90 minutes of ball milling,the powder particles consisted of fine lamellar micro structure on the order of micrometer,the particle size was about 30?m.The Cu-Cr25 alloy was prepared by.1280?liquid-phase sintering pre-alloying powder.Uniform refinement of the sample in the organization.The Cr particles in the matrix are composed of undissolved Cr and fine spherical eutectic Cr and a small amount of liquid-phase decomposition Cr-rich particles in the matrix.The hardness value of the alloy is 81.3 HV and the tensile strength is 272.599 MPa.The densification degree is improved and the electrical conductivity is 31.2 MS/m,and the comprehensive performance is excellent.Preparation of Cu-Cr Alloy Contact Material by Gradient Structure Method.The CuCr25 microcrystal powder was prepared by high energy ball milling,and the milling time was prolonged.The particle size of Cu and Cr was reduced.The solid solution of CuCr25 was improved and the Cu-Cr supersaturated solid solution was formed.The CuCr25 powder was milled in a ball mill and mechanically mixed with CuCr25 powder.The Cu-Cr25 composites were prepared by liquid-phase sintering.The microstructure of CuCr25 was finely grained and homogeneous.The microstructures of the surface microcrystals were 83.6 HV and the maximum tensile strength was 278.662 MPa.The densification degree of the composites was higher and the electrical conductivity of the composites was 33.2 MS/m.Based on these research,it is believed that material comprehensive performance is superior.